Automatic transmission



Jan. 27, 1948.

H. NUTT r-:r AL

AUTOMATIC TRANSMISSION Original Filed Jan. 4, 1941 5 Sheets-Sheet l Jan. 27, 1948. H. NUTTv r-:r AL Re. 22,967

AUTOMATIC TRANSMISSION Original Filed Jan. 4, `1941 5 Sheets-Sheet 2 Jan. 27, 1948. H. NUTT ET AL AUTOMATIC TRANSMISSICN OriginalFiled Jan. 4, 1941. 5 Sheets-Sheet 3 Jan. 27, 1948. H. NUTT Er AL Re. 22,967

y AUTOMATIC TRANSMISSION Original Filed Jan. 4, 1941 5 Sheets-Sheet 4 Jan. 27, 1948. H. NUTT Er AL AUTOMATIC TRANSMISSION 5 Sheets-Sheet 5 Original Filed Jan. 4, 1941 and Ressued Jan. 27, 1948 AUTOMATIC TRANSMISSION Harold Nutt, Chicago, Ill., and Richard L. Smirl,

Detroit, Mich., assignors to Borge-Warner Corporation, Chicago. Ill., a corporation of Illinois Original No. 2,332,593, dated October 26, 1943. Serial No. 373,201, January 4, 1941. Application for reissue November 22, 1943, Serial No.

This invention relates to automatic transmissions and particularly to automatic transmissions comprising a iluid device combined with gearing.

A large number oi.' automatic transmissions have been devised all of which may be classiiied into a relatively small number of types. Each type presents its own design problems and the completeness with which these problems are solved determines the amount of success the transmission will have in the field. One such fundamental type is the hydrodynamic or Foettinger" transmission which employs two or more vaned rotors coupled together through a fluid. 'I'he problem attendant upon the use of a hydrodynamic device in an automatic transmission include among others that of getting sufiicient torque multiplication to satisfy the requirements for an automobile and to do this at satisfactory efficiencies. This has led to the use of gearing in addition to the torque converter and to various clutching arrangements for substituting another drive for the torque converter at the speeds at which the torque converter is ineiiicient. With the addition of these devices the transmission becomes more complex and expensive.

Another problem encountered in the hydrodynamic type of transmission is that of operating an associated positive control element to effect a shift as, for example, from neutral to reverse. At idling speeds of the engine enough torque is transmitted through the hydrodynamic device to render the engagement of a positive toothed control device diilicult, if not impossible.

The principal object of this invention is to provide an automatic transmission which utilizes the advantages of a hydraulic torque converter and makes full provision for its several shortcomings with a minimum complexity of controls.

' Another object of this invention is to provide an automatic transmission of the hydraulic torque converter type in which a satisfactory reversing mechanism is employed.

Another object of this invention is to provide a simplified hydraulic system for operating an automatic transmission, the system including a clutch which utilizes the' pressure within the torque converter to change its condition.

Yet another object oi' this invention is the provision of improved means for starting an engine through the transmission by pushing the car in which the transmission is installed.

These and other objects of the invention will become apparent from the following description 11 (Cl. 'M -189.5)

when taken together with the accompanying drawings in which:

Fig. 1 is a plan view in section of the transmission.

Fig. 1a is a fragmentary section taken along line Ia-Ia of Fig. 1.

Fig. 2 is a schematic layout of the hydraulic system A Fig. 3 isa vertical section through the valve block taken along line 3-3 of Fig. 4.

Fig. 4 is a side view of the rear portion of the transmission showing the valves and a portion of the controls therefor taken along line 4-4 of Fig. 3;

Figs. 5 and 6 show the linkage for operating one of the valves inthe transmission; and

Figs. '1, 8 and 9 are schematic diagrams showing the operation of the manual over-control for one of the clutches.

Referring now to the drawings for a detailed description of the invention and particularly to Fig. 1, the transmission in its preferred form iscomprised in general of a drive shaft I0, a driven shaft I I, a hydrodynamic torque converter I2 located within bell housing I3, a valve block I4 secured to bell housing I3, a planetary change speed gearing I5, and a planetary reverse gear I6. Various clutches and controls are included for operating and controlling the torque converter and planetary gear-set including a positive clutch Il for locking up the torque converter. a hill brake I8 to be used in conjunction with torque converter I2, a brake I9 for conditioning planetary gear set I5 for overdrive operation, a roller and cam type automatic clutch 2l for conditioning planetary gear set I5 for direct drive, a releasable clutch 2| which may be released to disconnect the driven shaft II from planetary gear set I5 to provide a neutral, and a positive brake 22 of the toothed type for arresting one of the elements of the planetary gear set IE to provide a reverse drive.

The power is transmitted from drive shaft Il to a forging 23 bolted to a flange on drive shaft III, said forging 23 supporting in turn a flywheel 24 and a varied pump member 25 bolted to ilywheel 24. These last three elements form a chamber which is normally lled with fluid under pressure- Opposite vaned pump member 25 is a vaned turbine member 26 which comprises the driven element of the hydraulic torque converter I2. Torque conversion or multiplication is secured by means of a vaned stator 21 interposed between the exit of the turbine vanes and the entrance to the pump vanes. Turbine member 2E is riveted to a carrier 28. which Vis splined to brake al reacting against a plateau non-rotatably molintedinbellhmiing Il.

Carrier 2l is formed with radial bores 33 in which are moimted pistons 3l having at the outerwhich are adapted to engage slots II infforging Ii is etlected through, and the torque is multiplied by. torque converter I2. It will be noted that stator 21 is held against rotation by one way brake 3l as long as torque conversion takes place in the converter and that thereafter it is free to rotate Elfe impelloellnfzhe converter.

'For -the *next-fatiofdntchul isengaged to couple drive shaft Il directly with intermediate shaft 29 and thereby lock up torque converter l2. extremities thereof chamfered teeth-JSA-i-iFigflal lo The clutohmis rcentrifugaily conditioned for en- 'gag'einent considerably below the end pointrof the 23. VSaid listons Il are .hiaa'edstoiarwetraeted .torqoronuelsiomapie'ed of the converter, but it can-telengagedmtlthe will of the driver at any through a suitable opening' Il in' the carrien -A-Lepeedbovethisconditioned speed by momenintermediate shaft 29. The vchamferzonsteeth l5 is in such a direction 1.lzat:.wllen drve shtt` n 1s raming faster man mrmeaate'snafr u.. augment intermediate shaft 2i. but willl permit such clutching onswhen zthejpeed, of .'drlve shaft Il drops down to the speedof intermediate shaft-2l.

Intermediate shaft. 2! extends rearwardly-tn planetary` searaset-ll-:and drives .the carrier:V I! set. Upon carrier'llzaremonnted ltwhiehmhwith-afringgear 4l and with a sun gear l2. Said sun gearilzis formed tromfgaesleevefl which isziiangedind riveted to the rotatable element-A4. of brake'll.

l is splined fn a drum-which constitutes the driving; elementzof-dise clutch 2i, vthe driven elmnentr being splined todriven shaftll. Abosplinedtodrumisaconnect'- ing @sung nwmenmmrs the dnvernom:

drum 45 tothe simsean oi planetarygear set I'. Said Ysun gear-:lI-moshes withtplanetrgears I9 mounted m a carrier-il which is-ffreeto rotate about drivel shaft II. jPianeti-gears!! in to aiiange ilmtatablawith vdrivenshaftl-i.

The rotatable'eiement ofrerse brake 22 is comprised of `a toothed fmember 25|- bein thei'orm otanordinaryspurgeanmmmted to rotate withcarrier Il. :Beside driven shafti'l ,f

connection b:tween the drive anddriven'- shafts.

For forward speed inthe lowest'ratio, torque converter lockout clutch AFl Aiis-released, tzu-airesI Il and I! are released-andclutchi isengaged. The drive is then transmitted "from-drive-'shft III through the torque converter toin-termediate shaft 2l and thence-to planet gears Il of plane. tary gear seLIS. At this pointthe load oir Ythe driven shaft Il is transmitted-through clutch 2| turing gear Il and-aecordingly-sun-gearll will tend to 4rotate ahead of carrier 39. This, however; is prevented'by roller-and-camclutch l0 which locks the carrier to the-sun gear, thereby eil'ectinv direct drive throughpianetarygear set l5. Jn the-lowest-ratiomossible, -thereforeg-.the

throttle, thereby permitting vw 2 tionrtonccur. The ci chwiliremain intends above the een ugally conditioned speedmless forced back by the means .f.. the conditlons'to be hereinafter described.Y The pawls vll remain engaged below the `eonalditioned espeed -.so longV )as continuous torque is-beinztransmitted. Whenthe-vehicle is stopped; the torquebetween members'al -and .vwill reverseat-some point before the vehicle :comes to rhthlu enabling. the clutch to release automatically.

The next and highestfratio is obtained byenditioning. planetaryV gear seis l5 .for overdrive Will-.be described infdetaii later.

Reveme -isohtainedhy releasing clutches-l1-rand -li (the former releasing automatically when the car isst rest) and also brake- I9. Sprag 5I is toothed memberii to VYhold carrier 5l and rthe drive is therefore=-reversed through' planetary-gousset li, the drivebeing .through connectingi casting-Il to sun gear all.

The descxptiomthus far has been concerned merely with the forY transmitting the torque. from drive-shaft `Il Vtodriven shaft Il. The controls-tor effecting: the-various shirts-described'above-andothers Vtobe described hereinafter wl-l nowzbe-detailed.

With-.the exception oi=the sprag and the roller and cam devices the various clutchesand brakes are controlled, or operated and controlled, byhy draulicpressure. Y Theeontrolstherefor comprise iin the-main, pumosg-vaiv, and passages-so interconnected with thewarious clutches and brakes as tosupplyoperating pressm'efto-theproper device at the timedesiredand laisotoremove-:operating Y from'- certain: devices inanemergency and nnderfizhe-control o5 theoperatortoiefiect a down-shift. '.-Foroxample,'1neansareprovided for releasing brake Il ntoreduce the drive from overdrive indirect fdrtvesandadditional meanszare 'Providedxtorelease clutch 1II-to -restore the drive through-,the torque converter, both of these .down shifts being-.under the control'of thef'operator.

Referringmow tofFig. Vi2,- the various clutches and .brakes are shown schematically, together with the hydrauliecircuiis toand from theseelements and their respective control valves. Dual hydraulicsystems are provided, fluid pressurefor the first system v`being derived from'a pump 5i which is driven by means of gears 51 which in turn are driven from a sleeve!! drivingly connected to lmpellen'rember 25 of hydraulic torque converter 11.-* Pumpl therefore is operated whenever drive' shaft Il is turning. The oil from pump- 58V is maintained at a pressure of -approximately V60 pounds per-oq. inch byY means of 'a drivewbetwem: driven-haitillsandidrivenlahstt u intotwoeconduits' ltfadfl. In oon'duitlll is a reducing valve 94 which reduces the pressure in side outlet 65 to approximately 30 pounds per sq. inch. Oil at this pressure is then conducted through conduit 55 to a chamber 91 surrounding pump gear 51 and communicating through a passageway 59 with the interior of the hydraulic torque converter l2. It will be noted that the entire chamber formed by flywheel 24 and imi peller 25 is filled with fluid at 30 pounds per sq. inch pressure, which means that the outer surfaces of the pistons forming clutch I1 are acted upon by this pressure whenever pump 55 is in operation. As will be described in greater detail later. this pressure tends to assist springs 31 to retract the pistons to release the clutch I1 and is utilized to effect a down-shift of this clutch under certain circumstances.

A second branch 59 in pressure line 50 conducts iiuid at 60 pounds per sq. inch pressure to valve chamber 19 in which is located the control valve 1| for main clutch 2|. Said valve 1| has a central portion 12 of reduced cross section to permit the uid to pass therearound into conduit 13 which communicates with a central bore 14 located in shaft 29. Driven shaft contains a similar bore 15 in communication with bore 14 and conducts the fluid to an annular chamber 16 which is mounted for rotation with drum 45 of clutch 2|. Within annular chamber 15 is an annular piston 11 which is slidable axially to compress the driving and driven members of clutch 2l together and thereby couple driven shaft Il with drum .45 and its associated ring gear 4| (see Fig. 1).

Valve 1| is shown in the position it assumes when the transmission is conditioned for forward drive by the operator. The valve is slidable to the right to close oi! branch 59 and simultaneously to permit the fluid behind piston 11 to escape beyond the right hand edge (Fig. 2) of valve block |4. mented byl a retractor spring 19 (Fig. 1) which is fixed at one end 19 relative to chamber 15 and the other end of which bears against piston 11.

'Ihus when the main clutch control valve 1| is positioned as' shown in Fig. 2 and pump 56 is operated. iiuid under pressuregis conducted simultaneously to the hydraulic torque converter I2, to the outer surfaces of clutch pistons 34 of clutch I1, and to chamber 15 of clutch 2 |v to operate the latter clutch.

Under normal conditions fluid under 30 pounds per sq. inch pressure will be conducted through a branch 53 to a second valve chamber 8| in which is located a valve I2 for controlling the positive clutch l1. ,Said valve 52 is normally located to the right (shown in dotted lines) of the position shown in Fig. 2 so that the portion 83'of reduced cross section is in alignment with branch Eiland also with a side outlet I4 which communicates with a central bore Il in the forward end of intermediate shaft 29. lThis bore is in communication with opening 35 and conducts the iluid under 30 pounds per sq. inch pressure to the under side of pistons 34 of the torque converter lock up clutch l1. Pistons 94 are therefore balanced insofar as thc pressure within the converter chamber is concerned and are subject only to the action of centrifugal force on the one hand and the retracting action of spring 31 on the other hand. Said spring 31 is of such strength as to maintain pistons 34 in retracted position until the vehicle is moving at a speed of approximately 18 miles per hour. at which speed cen- This releasing action is aus'`- 6 trlfugal force overcomes the retractive eilort of spring 31 and moves the pistons radially out wardly to engage teeth 35 with slots 39. l

Thus when valve 1| is positioned as shown and valve 82 is in the dotted position, pump 56 being in operation. main clutch 2| will be operated and the hydraulic torque converter l2 will likewise be operated to transmit the drive at what corresponds to low speed from drive shaft I9 to driven shaft |I. Simultaneously, pistons 34 of clutch I1 will be balanced hydraulically but will be subject to centrifugal force, and when the speed of the vehicle becomes sufilciently great. clutch I1 will become operative to lock up the hydraulic torque converter and transmit the drive of drive shaft directly to intermediate shaft 29 instead of through the intermediary of the torque converter.`

To obtain the next and highest speed ratio through the transmission, clutch I9 is operated to arrest the rotation of sun gear 42. This is accomplished hydraulically by the second hydraulic system previously referred to, which is controlled by a piston type valve in the ilrst hydraulic system.

I'hc second hydraulic system is comprised of a pump 95 which is driven by gears 89 (Fig. l) drivingly connected to driven shaft so as to make pump 85 responsive to vehicle speed. The pressure of the iiuid supplied by pump 99 is maintained at approximately 50 pounds per sq. inch by a relief valve 81. It will be noted that this pressure is ten pounds less than that in the first system. A pressure line 99 conducts the fluid under pressure to a conduit 89 in valve block I4. Said conduit 89 is in communication at one end with branch 53 of the first hydraulic system, a valve 90 being interposed between the two systems. Said valve 9|) is free to move to the left a distance suilicient to uncover a side outlet 9| communicating with branch 92 in the iirst hydraulic system, and by this means, iiuid pressure may be supplied from the second system to the ilrst whenever the engine is not in operation and it is desired to eilect normal operation of the transmission. Thus when it is desired to start the engine by pushing the car, driven shaft will be rotated and will cause pump 8B to operate, which in turn will supply uid under pressure to conduit 59 and will move valve 90 to the left (Fig. 2) to uncover'outlet 9| and permit the iluid under pressure to enter the rst hydraulic system. After the engine begins to operate and pump 55 supplies fluid at 60 pounds per sq. inch pressure to branch- 53, the ten pound pressure differential will move valve 9| to the right until it strikes abutment 92 in conduit 89. In this position outlet 9| is blocked and a bleed outlet 93 is uncovered by means of a section 94 of reduced diameter in valve 99. A bleed opening 95 connects conduit 39 with bleed outlet 93 to prevent a rapid building up of pressure in the second hydraulic system after the car begins to move. The purpose of the delay in establishing a 50 pound pressure in the second system is to prevent the operation of the overdrive clutch I9 until a speed of approximately 18 miles per hour is reached. However, if pump 5B of the first hydraulic system is notin operation, valve 9U will be in its right-hand position (Fig. Z) and bleed opening 93 will be covered so that there is no delay in building up the pressure in the'rst system under these circumstances A9 is :an annular :piston 1M "mhichaismomhie Ssaidi'miember, 'l-"to 'ra'.frevers'e" 'position wherein f :spragiienagesaths'teeth ofmemberttciarrest the notation 'rot :planet carrier.

z Arm-| Urisf donnected'througlr-a'iink-l Ittofa tU/maimclutda'fva'ivevll. ||l is :naturel ohaiioating lelerfami iscsuppnrteixysa. ,-plate Urin-which isa slot I-It'for restrainingfthe :lever against -lateralemovemcnt with respectf :to

-axilly.-to compress tbe drivlngnnd:lirivemmemi .valve Il and-linkilll. The iulcrumfonle'ver H5 :while -the -delaywelve l-IlG-ixnlures.- thetr a qu pressure will he availablednr- -tu1l-..engegement. thereby preventing long. i Slip lieriods-nwhenfthe car isfbeing drivenfat a.-spced.whieh.-is appmni matelythe same as the cut-in speed.

iseprovidedtbv a roller Il mmmiecrunfplate lll.

` The connection with valve..||fcomprieea a-sieeve 12u whiohis slotted .at.|2| andi!! toreceive-the ,nppenend oilever |15. :A slottedplatezil engageaamotclr HG in lJeverl lI-landds .resilientLv .urgedtmthe right (Eig..1) .ima-spring |24 con- .tainedljn recess in -valve-.1l. A Because of the relativelocation oi.notch Ili--and-slotVY |2| the spring. pressure will Vtend torotate iloatinglever To recapitulate, the second hydrauliesywtem-is Q5 |5.in a' counter'clockwisedirectionl (Fig.- n but used primarily. to operateibrakeilftouestablish overdrive at. a ..particular= speed: if the driven shaft. It mavalso .be=used toupply difunde:- Apressure to therst Vhydraulic system if..for-;any

reason pumpe of-.theflrst system is -notin nplo eration and .it isldesiredto operate torquecnverter l2 and'clutch 2|'as ior.exam.ple, to start the engine by pushing the car.

' 'Thestator .brake Itis likewise operated-.hy fluid prssureand iscontrolled .by valveJll .in valveblock Il. Saidvalvef IDLis-'slidable inits bore to a left handpositionishowndotted inFlgn 2) wherein it ccnnectsa. Vbranch M2 f branch i! to a. conduit |03 bylmeans 01E-.a sectinnllllf reduced cross section. JWhenso moved, fuid under pressure is conducted to achamber 'lllof Vannular cross section in which'. is-disposedan annuiar'piston |08 whichis 'adapted' to compress the driving elementV IUT hd.releti0n'1emt 'of brakev I8 and'thereby arrest'the tottin ofist'ator 11. t'wll be'recalledfthtjat'spds' bov 118 miles `Aper'honr clutch'|1^is"operated to connect -pump -25and turbine '26 tgetherwhich 'reliwles statorl of' backward 'reactive'forceand said 21 --is then-free-"by' virtueel' the. o'nei-way holding characteristic of `brake "glffto" rutatein a' forward direction under tneiniuenceroi'the iluid'i the torque converter. Thifforwardruta tion-maybe arrested-by bypassingonevaybrake fll andrhdIding-sleeve Il threghrtssiinedcon'- -nection :with: driving Aerementl 01 =of 5rlie-""|8. -When so'held a'ptlwertul braking-mm -which in Akeepingffdowm thespeeit oithe vehicle.

.Having describedY the hydrauliwcirmtsefrbm the pumpto the variousAclutches-and bnakeaetbe means for controlling the valves Whicmimtmn control'the hydraulic circuits will no'w bedetiled.

Referringl particularly to' Eigsl 1," 2 'and .4, the fox-ward, neutral,nnd-reverse"control may comprise the usual leverinotshown) afthe steering wheel 'fof' 'the -automebilefwhich-is *confnected by snitablelinkake (riot' shown) toa-roek shaft Ill! disposedhverticlllyff the trhnsl'nsion -andimmediately below-spuug. fSid/ruekimft ,70

since'such-rottion will. berestrained. by link. Hl and arm.'|'|0,`the net result willbeto tend.to return vlvefll to'the. positionshown in Fig. 1,

i'. e.; tobias valve T I t'tlieilft.

It will benoted thtibecauseaf the-particular linkage employed it will .be necessary .tu Dass 'through' the "forward" positionzin order. to condition -the transmission for reverseL 'This causes clutch 2| to be engaged momentarilyeach time it is desired to advance Sprag 54 into toothed `member i3? JSince the crqat such time .is presumaniy standingr still; this-will have the effect 'of-momentarily' stopping toothed Amembert'thus 'preventing *unpleasant tcotn'ciashyand then re.

lcasingsaid tooth memberto'permil; thesprag to enter the teeth, 'if-for'anyvreason the teeth -hve .I-IS is providedY with two'ianns." ill-:andrlll I :th

connected immane-annoncent audslot'flihto Sheitan meheneked ma? #I which` tialiyiimpossihlethe ofspraglinto '.toothedxmember-l; isi-.eliminated '-iustjprlor -tc themctitinnfr reverse il and -asmooth operation of the reverse shiftlisfsured. *It will aisorbeiiibseedthtzthe. operation V(rtf clutch 2| :to-lmest thertatiuni of 'toothed member i3 is 11er-teeny :synchronized with. :the 'fxnevementof 1mi... f Y After.. :the' zhss been' conditioned 4forforwardsdrive rtheturques converter lock a up clutchetfldsautomatic'ailin operatedmnd in due 'course the everdrivedirakezds'likewisefoperated "Situationsfns however; where it is'neeessar-ytogshiftiout or overdriveintozdirect drivefinorderitoseeurethe benetrt the greater torquefmbtanabie imthis ratio. A The dmvn shift .maybe.eected by; the followingnstrumentali- Mes:

particuaflfly to' Figs. 3, .13,25* andi-8, chamber 99--assoeiated.withfoverdrive `brake :Il dis v rix-ovicied `with anutlet -5 e 1 1:25 -which communicatesmitha transverse bore-.|26 inv valve mock; I4. .1n-lame` mf is. located-f sfvaive nu ,which-is rotatable through-rant src oirrppmxi- .mateiyi sin-.one extrempitioniotavalve |21 conduit 25 isealgned withmlnt 12k in! the valve, r his witlxthehnmdnteriornl of the valve. The hollow interior communicates with a main vent |32 and also through a series oi openings |30 and an annular groove |3| in valve |21 with an auxiliary vent |32' leading to the exterior of valve block I4. The purpose of auxiliary vent |32 is to prevent leakage past the valve and shaft |33. In the other extreme position of valve |21, slot |28 is not in alignment with passageway and hence the pressure in chamber 09 is not ai'ected but is controlled solely by overdrive valve 95.

Valve |21 is provided with a stem |33'to which is pinned an ann |34. Said arm is in turn connected through a grasshopper type spring |35 to a second arm |35 rotatably mounted on stem |33 and connected at its free extremity through a rod |31 and associated linkage (not shown) to the accelerator pedal of. the automobile. Suitable stopslll and |39 are provided on valve block I4 to limit the angular travel of arm |34. It is undesirable generally to have the valve move with the accelerator pedal and accordingly spring |35 serves to prevent rotation of the valve to a downshifting position until the accelerator reaches its wide open position, whereupon an overcenter condition will exist as shown in Fig. 6 and spring |35 will be snapped to the left to the dotted position. The point at which this action takes place may be made apparent by the provision of a spring stop |440 which interposes a slight resistance to the movement of arm |35 to its overcenter position so that ii' the driver does not wish to down shift he will not depress the accelerator beyond the point of increased pressure. In a similar manner grasshopper spring |35 will prevent a return to overdrive until the operator substantially releases the accelerator pedal, which he will do naturally after he has no further need for increased acceleration.

Assuming that the vehicle is traveling at a speed at which clutch I1 is engaged but overdrive brake` I9 is not yet engaged. and the operator wishes to down shift to the torque converter. it will be necessary vto remove the fluid pressure v from behind pistons 34 in order to obtain a sumcient differential pressure to withdraw the pistons. Since clutch I1 is a positive clutch. .however. a mere differential in pressure will not be suflicient if an appreciable amount of torque is being transmitted through the clutch at the time. It will be necessary. in addition, to remove the torque for an instant from teeth 35 to enable the pressure differential to become effective. Accordingly the following mechanisms are employd to effect this down shift.

, Referring momentarily to Fig. 2 it will be observed that valve 82 controls the pressure behind pistons 34. In order to remove this pressure, valve 02 must be moved to the lei't tobockthe pressure side B0 and to vent conduit 04. Normally. valve 521s biased tothe right by a spring |4|. the movement to the right being limited by an arm |42 which moves with a rock shaft |43. As shown in Fig. 1. rock shaitf|43 is provided -with an arm |44`which is connected by suitable .linkage |45 to the accelerator pedal or to some other manual control (not shown). desired to down shift into the torque converter,

Whenit is the control is moved and this movement is transmitted through linkage |45. arm |44, rock shaft |43 and arm4 |42 .to valve 02, thereby moving the valve tothe leftagainst the action of spring Ill- (Fig. 4). This removes pressure from behind pistons 34 and establishes the pressure dinerential which will beutilized torelease the clutch.

'the torque on teeth 35. The current for the ignition circuit |45 is derived from a battery |41, or other source of electrical energy, and a coil |48, the circuit through which is interrupted periodically in timed relation to the movement of the crank shaft of the engine through an interrupter |45. Connected in shunt with theA circuit through the interrupter I 49 is a second circuit |54 which includes a switch |50 mounted on a pivoted bell crank 5|. The condition of the shunt circuit and control therefor during normal operation of the automobile is shown in Fig. 9. It will be observed that switch |50 is normally closed and completes the circuit up to a dash pot |52. In said dash pot |52 are contacts |53 and |54 which are mounted on springs extending laterally inwardly from the sides oi' the dash pot. Opposite contacts |53 and" |54 are contacts |55 and |55, respectively, connected together electrically by means of a spring support |51. A pin |50 controlled by spring |59 and piston |50 normally bears against the support for contact |53 to make the circuit betwen contacts I 53 and |55. and to break the circuit between contacts |54 and 55. Under normal conditions, therefore, shunt circuit |54 is broken by the separation of contacts |54, 55, and interrupter |45 controls the circuit.

In order to cut the ignition it is necessary to keep the primary circuit shorted by completing 82 which controls positive clutch |1. For this reason, the mechanical movements of switch |50 are controlled from the same linkage |45 which controls valve 02.

Assuming that the control for valve 82 has been operated to down shift into the torque converter, bell crank |5| is rotated clockwise to the position shown in Fig. 1. It will be noted that lower contact |5| is mounted on a spring which is just suiilciently long to catch a washer |52 mounted on the end of a rod |53. which in turn is 'connected to piston |50. The clockwise movement of' bell crank |5| will therefore raise piston |50 and lsimultaneously break the circuit through switch |50 and through contacts |53 and |55, the latter by reason of the raising of contact |53 from contact |55. At the same time the circuitswill be made through contacts |54 and |55. Upon continued rotation of bell crank |5| in a clockwise direction. washer |52 will be freed and piston |50 will descend toward contacts |53 and |54. The freeing of washer |52 will also cause the circuit to be completed through switch |50. Downward movement of the. piston will be retarded due to the dash pot action, and a pre- 'determined time interval will elapse between a ment will break the circuit through contacts |54 and 55.` During the interval in which" the shunt circuit is in the condition shown in Fig. 8,torque willbe removed from teeth 35 and. the pressure having been previously removed from behind the pistons', said pistons w/ill be retracted under the medi.;

- Il combined influencent the :pressure within-s the turque-converter.' and therretractivc: 0! springs 3l; The duration-of.` the.v shortius 'fot the circuitzfis 'only a matterrfoiaf fewr'explosions r of the'fengine; so that the runningaof: thmenginezis not seriously afiected` a' It-= willfbe notedfthatfshuntchcuit:I8# inestablishnedflnldssh pot vIM on theyupwardfmovement of.A .pistou i60 las.x well- .as :on its downwardwmove,

ment-'.andfhence; fwereit not forlswitch.: Ille the. l0;

ignition: circuitlwould-.bmshunted and thegtnrque removed from'pistonsflhbefore -theuid had an: opportunityftofescape.. fromrfbehhid: the? pistonsy Switch IIBllJs..soconstructed;however?,tthilfirit happened. .lkbegine to waveband:

will Aremaixn open ,drniz'lgfv thecentire. interval; ln.- whichithezshunt. ycircuit lisxmnrlletiad:through thm dash pot. This is accomplished. hyrmakingxreturn,

Vic* lrmlraulic-V system deriving` its" power 'ritorni the drivosshaft fon-controlling someof saidedevices- 1de. ther meetings device.

spring |59. stronger v.than thespringenlpnorting I contact L61y ofswitch I 50. .y Thectual:

of the-ignition .eircuit\is, therefore rlimited yto the.

return-'movement of-pist'on l6n..-whieh provides.

sl-luxitins` m.

' ignitioncircuit. .may be approximatelzyh'alf a..

second..- The dilratio'njof thehunti canebepre.- determined byanproper relation between the.V strength. 01.'. return spring i591 thelilid leak'.

in the. dash not so .as not to.exce'ed;lfcr'exampie,. sus

onefquarter ofa. second; Plstons 34" are'subject tolcentrifugalfforce...

` which varies as the. square' loithe speedfof the s vehici... .The size'iof the pistons'. andthe ,magniy tude i'of' the., retractivc. ,eiort the';unbalanced?hydraulic pressuregmay .he so.; predetermined esito prevent' the. retraction of; the pistons kat speeds at .whlchztorque 'multiplicatitimthrough the converterz I 2'is'no, 1onger possible, since at`-such speeds no advantage can V`1,r)e. gained by. driving through the converterinstead ofthrough'the clutchV I1.'

It: is understood. that 5 the fsteneraxbearings; g and-"gaskets necessary' for. the. operation. of a, device ofthe class described maybeV arranged, to suit' thedesigner and accordingly are not described 'herein in` detail. thatthe foregoing-description is merelyillustra.- tive of* e" preferred` embodiment* endfthativ the scope 'of the invention -therefor is `notto 'be-'lime ited thereto butv is `to berdeterrnined by'the ap- 4 pendedclaims.

Lof :springs ...-311 andra@ In is .understood further j i' A4transii'rissiorrcorrrprisirngofl drive shaft, af'

driven shaft; torque convening'mechanis'm re. versing mechanism of vth'e'diffe'reiitial'tinsrel-hiivinrgl, atieastrthree cooperating'elemerrts: orierofjsaidi elements being connected-" to the driverrjshaitgj means `connecting the torquemonverting mechanismwith the-driving shaft;means'coi'xtirruously;Y means bemmesmctive and is;

eiective toconnect the torque' converting:mecll v anism with another of`said" elements, releasable means connecting `the .torque ,converting j mecha;

leasable connection. before. th

third 'elementi is arrested.

ZIA .transmission comprisingA driving and" drivenshafts; hydraulically controlled devices for connectingtlie shafts .indi'ernt sneed ratios; pg 7a.

.l tiommeans such soeiating.` the secondi, element .--.3i :A;-.transmission:. corrrnrisingnl dmcshatt: s driverrrshaihatorque; conv acreversi-ngmechanism connected .-:dnzseriesbetween the. shafts;saidrreversingmechanimrzcomprising a 'plurality of relatin1y-rotatable-elemente onerof which -isrnon-releasably connected: to Ithe* driven? shaft, f. rotationeoi'ffa seeondflelement' and:V latine'. the. movement: orfai means: for retate the; arrestfof. thswsecondelementr wh drivenislnftrisznotzrotatd.' o

4V.. -As transmission `fori .faz-vehicle fcompr-ising e drive, shaft. La# driven shaft wheels.- of the vehiee -nndf lation therewith,A torque connectedzbetweensaid. ferentiel gearine hsvi tottherdrivenlshaft, the. .-trensmission.. iseconditioned for nevercezv for: arresting; thefrotationaoi lx1-second frictionxmeans eflecti in` motion iorf.

en: themnvabledn timed reshafts and including difng; omr-element:connected element vie-.when thvehicle is not arresting the rotationtoi thesecondielement, through the intermediaryofra third :element for. assisting: the.. operationr ofthopositiveearrestings means.:

5. A,..transmission co mprisingra-drive shaft; a drivenishafhitorque c onvcrtingmechanismcon'- nectedbetween said shafts. and includngfplane.- tary.gearingihavingfa,,ring-gearr connectedto the driven ..sha.ft,.a f. carrier and, a: means operable. .whenthetran arrest .the .rotatiomtherecf .andffriction means co- `operating through. the; intermedias-yaoi the sun geen andthe drivenlshaft the ,rotatiomof .thecarrier to, facilitate the en gagement, ofthe positivemeans.

6'..A transmission .claim 4," andcontroimeansior the positive. means and for the Vfriction.meansy.saidcontrol.en'eting a. .sequentialmovement of theposiive and fric- '.thatduringtherst portion of of. tha-.controLmeans the friction their. released just prior-tethefenegcment cffthefnositivetmeans.

7;: A-transmission for 'l ai vehicle: drive: shaft; ad-rivenrshaft; and mechanism theJmovement torque converting rotationoi'awhichmay-rhe arrested-to eiect a speechl change through .they mechanism; positiveA meansfi'orfarresting the rotatio'nof the' element, a secondi-element; Huid-controlled meansfor aswith the :driven shaft :rnd-'With` the-'rsth'mentioned element. to relate theA movement or'lack'otmovement of the driven-shaft to themovement of the `rstmen flll'ecleienrxined ons siiwperiod in.

v positive@ means: forarresting-l the thirdgelement-.ta the zjimovementcf the drivenfshaftmherebyz to facili- -ted; with l the converting mechanism'V positivemeans operablewhenr z and Sun. geareim'iiitiverA v Snrissiondszccnditloned for-..revers e; for,.engaging:the.carrier to.

.to .assist .imm-resting ifor` a vehicle as .described in :comprising ai.

rcormectedbetween said shafts' said. mechanisnrzfiriciimdingrazrctdtabl element'A the honed-element;- andorvaivezcontrqllingtne fluid 13 means, said valve being mechanically connected to the positive arresting means.-

8. `A transmission as described in claim 1, said valve having portings which permit the fluid controlled means to operate upon the initial movement of the positive means in its arresting movement and which release the fluid controlled means `iust prior to the engagement of the positive means. 4

9. A transmission comprising a drive shaft, a driven shaft, torque converting mechanism connected to the drive shaft, a ring gear connected to the Adriven shaft, a sun gear non-releasably connected to the said mechanism, planet pinlons meshing with the sun and ring gears, a carrier for the planets. a toothed element connected to the carrier, a cooperating toothed device for engaging the toothed element to hold the said element against rotation. a clutch for connecting the torque converting mechanism to the drivenshaft, fluid means for operating the clutch, a valve for controlling the iluid means. a manual control element, and means connecting the control element to the toothed device and to the valve to cause the valve to move in timed relation to the toothed device, said'valve having portings which cause the clutch to engage prior to the engagement of the toothed device with the toothed element to lock the carrier and its associated toothed element to the driven shaft and then release the clutch immediately before the toothed device engages the toothed element.

10. In la torque transmitting Amechanism for a prime mover having a speed regulator, fluid control means fortransmitting the torque of the prime mover, a valve for controlling' the iluid means, and means connectingthe valve to the speedregulator, said means including an overcenter device i'or preventing a movement of the valve except at the extreme positions of the speed regulator. and said overcenter device comprising a pivoted arm connected at its free end to the speed regulator, an arm connected to the valve, and a compressible medium connecting the arms, said arms being adapted to swing past one another to alternately compress and release said medium.

11. In a torque transmitting mechanism for a prime mover having an ignition system, means for multiplying the torque of the -prime mover, positive clutch means in parallel with the torque multiplying means, said positive clutch means having a movable element for controlling the engagement and disengagement thereof, means for impressing a force upon the movable member of the clutch while the clutch is in engaged condition, said force being applied in a direction to release the clutch such that pending the release of torque on the clutch itself the releasing force is ready to move the clutch to released position, and means for relieving the torque on the clutch when the releasing fo'rce is established, said torque-relieving means comprising a normally broken circuit in parallel with the ignition circuit. means for establishing the circuit, and mechanical means controlling the circuit establishing means.

12. In a torque transmitting mechanism for a prime mover having an ignition circuit. a positive coupling device, means for establishing a releasing bias on the device, means for relieving the torque on the device comprising a normally broken circuit in parallel with the ignition circuit, means ior establishing the normally broken circuit, dash pot means for controlling the operation of the circuit establishing means, and means for coordinating'operation of the bias establishing means with the operation of the dash pot.

.v 13. Ina torque transmitting mechanism for a prime mover having an ignition circuit, a positive ,coupling device-pressure differential means for releasing the device, means for relieving the torque -on the device comprising a normally broken circuit in parallel with the ignition circuit, means for establishing the normally broken circuit, dash pot means for controlling the op eration of the circuit establishing means, and means for simultaneously operating the pressure differential means and the dash pot. said dash pot delaying the establishment of the normally broken circuit to permit the pressure diiierential to be effected.

- 14. In a power transmission system having an ignition circuit which is shimted under predeter- 4mined conditions to facilitate a speed ratio change, a plurality of pairs of contacts in sexies in the shunt circuit, a reciprocable plunger for controlling the sequence ci' operation of two of said pairs of contacts, means for limiting the effectiveness of the plunger to control the contacts to the return stroke thereof, and dash pot means controlling `the speed ofthe plunger on its return stroke to time the shunting of the ignition circuit to the speed ratio change.

15. In a torque transmitting mechanism for a prime. mover having an ignitionV system, said mechanism having a positive .coupling device which is releasable under the combined inuence of a pressure dierential means biasing the de vice to released podtion and torque relief resulting from an interruption in the ignition system,

second switch arm having a contact thereon, a

third switch arm -having a contact normally spaced from the contact on the second switch arm and another contact normally in engagement with the contact on the first switch arm, means for rotating the pivoted arm whereby to latch the rod to pull said rod and its associated piston through said cylinder, said arm contacts being separated throughout this movement and the contacts on said switch arm being ilrst made and then reversed, said md becoming unlatched at the end of the movement to remake the contacts on the arm. and rilient means to return the piston, said piston ilrst consuming sulcient time prior to its striking the ilrst switch arm to enable the releasing bias to be established on the positive device, then remaking the separated contacts on the ilrst and third switch arms to complete the circuit and thus interrupt the ignition circuit, thereby relieving the device of torque, and ilnally breaking the contacts on the second and third switch arms to restore the system to its original condition.

16. A transmission comprising driving and driven shafts, hydraulically operated devices for connecting the shafts in diilerent speed ratios, a hydraulic system for controlling some of said devices only, a second hydraulic system for controlling at least one device notV operated by the ilrst system, said systems being operated at different pressures, and a pressure-diilerentially 

